Mechanical pencil, especially for thin leads

ABSTRACT

A mechanical pencil, especially for thin leads, in which a tubular lead guide projects from and is guided for movement in axial direction in one end of a tubular casing. A resilient lead clamping arrangement is located within the casing spaced from the tubular lead guide and having clamping portions normally resiliently biased to be out of engagement with a lead passing therethrough. Transmission elements are provided between facing ends of the clamping arrangement and the lead guide to transmit, during writing and exerting of an axial pressure on the lead guide tending to move the latter into the casing, to the clamping arrangement a force which is multiplied so as to move the clamping portions of the clamping arrangement into clamping engagement with the lead, to thereby prevent inward movement of the latter during writing.

Feb. 4, 1975 1 MECHANICAL PENCIL, ESPECIALLY FOR THIN LEADS [76] Inventor: Kemal Butka, 372 Central Park West, New York, NY. 10025 [22] Filed: Nov. 29, 1973 [21] Appl. No.: 420,172

Related US. Application Data [63] Continuation-impart of Ser. No. 333,148, Feb. 16,

1973, abandoned.

2/1963 Johnson 401/53 1/1969 Schischkow 401/53 Primary Examiner-Lawrence Charles Attorney, Agent, or Firm-Michael S. Striker [57-] ABSTRACT A- mechanical pencil, especially for thin leads, in which atubular lead guide projects from and is guided for movement in axial direction in one end of a tubular casing. A resilient lead clamping arrangement is located within the casing spaced from the tubular lead guide and having clamping portions normally resiliently biased to be out of engagement with a lead passing therethrough. Transmission elements are provided between facing ends of the clamping arrangement and the lead guide to transmit, during writing and exerting of an axial pressure on the lead guide tending to move the latter into the casing, to the clamping arrangement a force which is multiplied so as to move the clamping portions of the clamping arrangement into clamping engagement with the lead, to thereby prevent inward movement of the latter during writing.

8 Claims, 5 Drawing Figures PATENTEU FEB 5 SHEET 1 [1F 2 PATENTED FEB 75 SHEET 2 BF 2 MECHANICAL PENCIL, ESPECIALLY FOR THIN LEADS CROSS-REFERENCE TO RELATED APPLICATIONS This is a continuation-in-part of my application Ser. No. 333,148, filed on Feb. 16, 1973 and now abandoned BACKGROUND OF THE INVENTION Mechanical pencils are known in which the lead is protected against breaking by means of a tubular lead guide which projects beyond one end of the tubular casing of the pencil and which surrounds the lead substantially up to the writing point thereof. Such pencils are especially adapted for use with thin and/or soft leads, for instance with leads which have a diameter of 0.5 or 0.3 mm, and which are eventually also rather soft. Such pencils with thin leads make it possible permit to draw, respectively to write, with fine or heavy lines which is possible with mechanical pencils using relatively large diameter leads and with wooden pencils, only if the leads are carefully sharpened. Such repeated careful sharpening of the lead is, however,

avoided with thin-lead mechanical pencils.

A disadvantage of mechanical pencils of the aforementioned kind is that the position of the lead relative to the lead guide has to be repeatedly and exactly adjusted since the lead will not write any longer when its end projecting beyond the lead guide is used up, and since if the lead extends too far beyond the leadguide it will easily break, and that therefore the adjustment of the position of the lead relative to the lead guide must be made much more carefully than with mechanical pencils of the usual heavy lead type.

An attempt has already been made to avoid the aforementioned disadvantage by a construction in which the lead guide is not fixedly connected to the casing, but is mounted in the lower end ofthe casing for movement in longitudinal direction, and wherein the lead guide engages the lead with a predetermined frictional force which is chosen in such a manner that the lead will be moved relative to the lead guide by a small pressure, for instance by engagement of the lead guide with the writing surface or by an advancing movement of the lead.

During writing or drawing, the lead will be pushed back by the pressure exerted thereon so that practically only the end face of the lead, that is the acting writing face thereof will project beyond the tubular lead guide. As the lead is used up, the lead guide will come into contact with the writing surface and will thereby gradually be pushed back into the pencil casing, so that only the end face of the lead will remain in contact with the writing surface, whereas the portion thereof projecting beyond the pencil casing will be surrounded and thereby protected by the non-bendable tubular lead 'guide.

Thus the necessity of repeatedly adjusting the lead is avoided, and the position of the lead has to be adjusted only when its whole length projecting beyond the lower end of the casing is used up.

SUMMARY OF THE INVENTION It is an object of the present invention to further improve mechanical pencils, especially for thin leads, in such a manner to obviate completely the necessity for adjusting the lead.

It is a further object of the present invention to provide for a mechanical pencil, especially for thin leads, in which the clamping mechanism for the lead in the interior of the tubular casing occupies only a small part of the interior of the casing so that the remainder thereof may be used as a storage space for additional leads. The storage space. respectively its lower end. is preferably in this case constructed in a manner known per se to automatically advance a new lead into the clamping mechanism when the lead in use is used up to such an extent so as to provide in the clamping mechanism room for reception of a new lead. The leads may be arranged in the storage space in two stacks or in a plurality of stacks superimposed upon each other.

With these and other objects in view, which will become apparent as the description proceeds, the mechanical pencil according to the present invention. especially a mechanical pencil for thin leads, mainly comprises an elongated tubular casing means having a .lower end, resilient clamping means arranged substantially coaxially within the casing means spaced from the lower end thereof and movable between a normally open position in which it is disengaged from a lead passing therethrough and clamping position in which it clamps the lead. The clamping means includes a connecting portion remote from the lower end and a plurality of circumferentially spaced force-multiplying arms which extend from the connecting portion towards the lower end and define in the region of the connecting portion a lead passage. The tubular lead guide means projects axially beyond the lower end of the casing and is constructed for frictionally engaging a lead passing through the clamping means and tubular lead guide means. Transmission means are arranged between the tubular lead guide means and the clamping means for transmitting during writing and exerting of an axial force and slight inward movement of the tubular lead guide means a corresponding pressure to the arms of the clamping means to move the latter to the clamping position in which the arms multiply the applied force and engage the lead in the lead passage with an increased force, so as to prevent inward movement of the lead. Restoring means serve to move the lead guide means upon cessation of axial pressure thereon in outwardly direction while the clamping means returns again to the open position. The mechanical pencil preferably includes also cooperating stop means on the casing means and the lead guide means for limiting outward movement of the latter relative to the casing means.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side view of the automatic pencil according to the present invention;

FIG. 2 is a partial axial cross-section through the pencil shown in FIG. 1 and drawn to an enlarged scale;

FIG. 2A is analogous to FIG. 2, but illustrates a modification',

FIG. 3 is an exploded isometric view of the clamping means of the pencil and the transmission means cooperating therewith; and

FIG. 4 is an axial section through the clamping means of FIGS. 2 and 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing and more specifically to FIGS. 1-4 of the same, it will be seen that the mechanical pencil according to the present invention comprises tubular casing means including a substan: tially cylindrical tubular casing part to the lower end of which a slightly conical tubular part 7 is connected, preferably releasably, by means of a threaded connection 10a as clearly shown to FIG. 2. A storage space 11 for storing a plurality of leads is provided in the upper portion of the substantially cylindrical casing part 10, as clearly shown in FIG. 2, and the bottom wall of the storage space 11 is formed by a central projection 9 re tained between shoulders 10b and 9e, and shoulders 70 and 9c. The upper surface of the projection 9, which constitutes the bottom wall of the storage space 11, is curved towards the center thereof so that leads in the storage space 11 will automatically slip into the bore 9 when a lead located therein is used up to permit movement of a new lead into this bore. The upper end of storage space 11 may be closed by an eraser l2.

Clamping means 8 are coaxially arranged in the portion 7. The clamping means 8 have an upper annular portion 8d and a plurality of elongated resilient arms which are integral with the annular portion 8:] and project downwardly therefrom circumferentially spaced from each other. Each arm has a portion 80 adjacent to the portion 8d, and a portion 800 projecting axially beyond the associated portion 8c. The portions 80 define a lead passage through which a lead 1 can pass with small clearance. The portions 8cc define a passage of substantially greater diameter. Each of the portions 8cc has a free end provided with ajaw having two inclined prefaces 8a, 8b which face in mutually opposite axial directions. The arms 8c, 80c are resilient and are biased in such a manner so as to be normally in an open position in which the portions 80 thereof are disengaged from a lead passing centrally through the clamping means 8.

The portion 7 of the casing means of the pencil is formed at the lower end thereof with a stepped bore forming a pair of annular shoulder faces 7a and 7b, and the tubular lead guide means which projects with a portion thereof beyond the lower end of the portion 7 comprises an outer substantially rigid sleeve 2, the outer surface of which is likewise stepped so that the sleeve is slidably guided in the stepped bore of the portion 7 and is provided with corresponding shoulder faces 2a and 2b adapted to engage the shoulder faces 7a and 7b so as to limit the outward movement of the sleeve 2 relative to the portion 7. The bottom end of the sleeve 2 is slightly inwardly curved at 20, as clearly shown in FIG. 2, and surrounds a lead 1 passing therethrough with a very small clearance. An inner tubular lining 3 of slightly resilient material, such as rubber or plastic, is located in a space found between the inner surface of the sleeve 2 and the outer surface of a lead 1 passing therethrough, which space is the result of partial recessing of this inner surface, and this lining 3 frictionally engages the outer surface of the lead I so as to take the latter along during outward movement of the lead guide means comprised by the sleeve 2 and the inner lining 3.

Transmission means are located between the upper end of the tubular lead guide 2 and the lower end of the clamping means 8.

These transmission means preferably comprise a member 5 having an annular portion 50 adjacent the lower end of the clamping means 8 and two oppositely projecting tubular portions 5b, 50 which extend from the portion 5a as shown. A biasing spring 4 can be seen in FIG. 2 to be interposed between and in engagement with the underside of the portion 5a and a bottom wall 2d in an axial recess R of sleeve 2, respectively. Spring 4 may be replaced by an elastomeric tubular member 4, as seen in FIG. 2A.

.The surface 8a of the clamping jaws is juxtaposed with an endface 9a of the tubular extension which projects from the portion 9a and surrounds the arms 8c, See. The surface 8b, on the other hand, is similarly juxtaposed with an endface 5d of the tubular portion 5a.

The above-described mechanical pencil will operate as follows:

When not in use, the various elements of the pencil will be substantially in the position as shown in FIG. 2, whereby the cooperating stop faces 2a and 7a or 2!) and 7b on the sleeve 2 and the casing part 7 will be slightly spaced from each other, or else engage each other while the coil spring 4 and/or the element 4 is in the fully extended (i.e., relaxed) position. The endfaces 8a, 9d are slightly spaced from one another as are the endfaces 8!), 541. Thus, the clamping means 8 will be in the open position, that is the arm portion 8c will be disengaged from the outer surface of a lead 1 passing through the clamping means and the lining 3 of the tubular lead guide means. During writing or drawing the end 2c of the outer sleeve 2 will engage the writing or drawing surface so that the sleeve 2 will be pushed inwardly into the casing portion 7, with a force P thereby compressing the element 4 and/or 4' and causing the member 5 of the transmission means to move correspondingly inward. This results in engagement of the endfaces 8a, 9d and also of the endfaces 8b, 5d. Thus, as clearly shown in FIG. 4, a force component P, causes the arm portions 8cc to be moved radially inwardly.

This force component P, will be multiplied by the appropriate lever arm (three times in FIG. 4) and act as force component P to press the arm portions 8c against the outer surface of the lead 1, thereby preventing an inward movement of the sleeve 2. When the free end of the lead projecting beyond the end 2c of the sleeve 2 is used up, then it is sufficient to briefly disengage the end 20 of the sleeve from the writing or drawing surface. which disengagement will in any case automatically occur at the end of a written word or a drawn line, and the compressed spring 4 and/or member 4 will thereby return to its expanded position, pushing the sleeve 2 outwardly while the faces 8a and 9d and the faces 8b and 5d become slightly disengaged from each other, resulting in a return of the clamping means 8 to the open position so that the lead is free to advance. The friction between the lead 1 and the lining 3 must be great enough to assure that the lead is advanced when the lead guide means 2, 3 moves outwardly of the casing part 7 during expansion of the member 4 and/or 4' and simultaneous movement of the clamping means 8 to the open position. On the other hand, the friction between the lining 3 and the lead 1 must be small enough to permit easy movement of the sleeve 2 and the lining 3 thereof relative to the lead 1 during application of normal writing pressure. The elements of the disclosed automatic pencil will therefore cooperate with each other to assure automatic feeding of a lead into the tubular lead guide means with the end of the lead slightlyprojecting therefrom until all of the leads in the storage space are used up, while the respec-, tive lead in use will be protected by the tubular lead guide means 2, 3 against breakage.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of mechanical pencils for thin leads differing from the types described above.

While the invention has been illustrated and described as embodied in a mechanical pencil for thin leads with an automatic advancing mechanism for the leads, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. In a mechanical pencil, especially for thin leads,'a combination comprising elongated tubular casing means having a lower end; resilient clamping means arranged substantially coaxially within said casing means spaced from said lower end and movable between normally open position in which it is disengaged from a lead passing through said clamping means and a clamping position in which it clamps said lead, said clamping means including a connecting portion remote from said lower end and a plurality of circumferentially spaced force-multiplying arms extending from said connecting portion towards said lower end and defining in the region of said connecting portion a lead passage; tubular lead guide means projecting coaxially beyond the lower end of the tubular casing means and being guided therein movable in axial direction, said tubular lead guide means being constructed for frictionally engaging a lead passing through said clamping means and said tubular lead guide means; transmission means between said tubular lead guide means and said clamping means for transmitting, during writing or drawing and exertion of axial pressure and slight inward movement of the tubular lead guide means. a corresponding pressure to said arms of said clamping means to move the latter to said clamping position in which said arms multiply the applied force and engage the lead in said lead passage with an increased force, so as to prevent inward movement of the lead; and restoring means for moving said lead guide means upon cessation of said axial pressure in outward direction relative to said casing means while said clamping means return to said open position thereof.

2. A combination as defined in claim 1, and including cooperating stop means on said casing means and said lead guide means for limiting outward movement of the latter relative to said casing means.

3. A combination as defined in claim 2, wherein said connecting portion is an annular portion and said arms each have a free end remote from said annular portion and formed with a plurality of elongated resilient projecting portions integral with the respective arms and having surfaces adapted to be engaged by said transmission means and being inclined transverse to the longitudinal axis of said casing means in the direction of said axis.

4. A combination as defined in claim I, wherein said resiliently expandable and contractable transmission means constitutes also intermediate guide means for guiding with small clearance a portion of a lead between said clamping means and said tubular lead guide means.

5. A combination asdefined in claim 1, wherein said arms each have a first portion projecting axially from said connecting portion, said first portions together defining said lead passage, and a second portion projecting axially from the respective first portion, each of said second portions having a free end provided with an endface directed towards said transmission means and being inclined outwardly of and rearwardly relatively to the axis of said casingmeans, said transmission means comprising a rigid member having a contact face adapted to engage said contact faces for moving said second portions inwardly towards said axis with a force which is multiplied and transmitted to said lead by said first portions.

6. A combination as defined in claim 5, wherein said end portions-each has an additional contact face directed towards said connecting portion and inclined outwardly of and forwardly relative to the axis of said casing means; and further comprising a tubular portion fixed to said casing means axially inwardly of said clamping means and outwardly surrounding the latter with slight clearance, said tubular portion having a front endface rearwardly adjacent said additional contact face, and said clamping means being movable slightly axially inwardly of said casing means in response to similar movement of said lead guide means.

7. A combination as defined in claim 1, wherein said tubular lead guide means comprises an outer sleeve and an inner tubular lining of a material for frictional engagement of a lead passing therethrough.

8. A combination as defined in claim I, wherein said casing means has an upper portion forming a lead magazine, said lead magazine having a bottom wall provided with a coaxial extension and formed with a bore for passage of a lead therethrough, said lead passage of said clamping means being in registry with said bore. 

1. In a mechanical pencil, especially for thin leads, a combination comprising elongated tubular casing means having a lower end; resilient clamping means arranged substantially coaxially within said casing means spaced from said lower end and movable between normally open position in which it is disengaged from a lead passing through said clamping means and a clamping position in which it clamps said lead, said clamping means including a connecting portion remote from said lower end and a plurality of circumferentially spaced force-multiplying arms extending from said connecting portion towards said lower end and defining in the region of said connecting portion a lead passage; tubular lead guide means projecting coaxially beyond the lower end of the tubular casing means and being guided therein movable in axial direction, said tubular lead guide means being constructed for frictionally engaging a lead passing through said clamping means and said tubular lead guide means; transmission means between said tubular lead guide means and said clamping means for transmitting, during writing or drawing and exertion of axial pressure and slight inward movement of the tubular lead guide means, a corresponding pressure to said arms of said clamping means to move the latter to said clamping position in which said arms multiply the applied force and engage the lead in said lead passage with an increased force, so as to prevent inward movement of the lead; and restoring means for moving said lead guide means upon cessation of said axial pressure in outward direction relative to said casing means while said clamping means return to said open position thereof.
 2. A combination as defined in claim 1, and including cooperating stop means on said casing means and said lead guide means for limiting outward movement of the latter relative to said casing means.
 3. A combination as defined in claim 2, wherein said connecting portion is an annular portion and said arms each have a free end remote from said annular portion and formed with a plurality of elongated resilient projecting portions integral with the respective arms and having surfaces adapted to be engaged by said transmission means and being inclined transverse to the longitudinal axis of said casing means in the direction of said axis.
 4. A combination as defined in claim 1, wherein said resiliently expandable and contractable transmission means constitutes also intermediate guide means for guiding with small clearance a portion of a lead between said clamping means and said tubular lead guide means.
 5. A combination as defined in claim 1, wherein said arms each have a first portion projecting axially from said connecting portion, said first portions together defining said lead passage, and a second portion projecting axially from the respective first portion, each of said second portions having a free end provided with an endface directed towards said transmission means and being inclined outwardly of and rearwardly relatively to thE axis of said casing means, said transmission means comprising a rigid member having a contact face adapted to engage said contact faces for moving said second portions inwardly towards said axis with a force which is multiplied and transmitted to said lead by said first portions.
 6. A combination as defined in claim 5, wherein said end portions each has an additional contact face directed towards said connecting portion and inclined outwardly of and forwardly relative to the axis of said casing means; and further comprising a tubular portion fixed to said casing means axially inwardly of said clamping means and outwardly surrounding the latter with slight clearance, said tubular portion having a front endface rearwardly adjacent said additional contact face, and said clamping means being movable slightly axially inwardly of said casing means in response to similar movement of said lead guide means.
 7. A combination as defined in claim 1, wherein said tubular lead guide means comprises an outer sleeve and an inner tubular lining of a material for frictional engagement of a lead passing therethrough.
 8. A combination as defined in claim 1, wherein said casing means has an upper portion forming a lead magazine, said lead magazine having a bottom wall provided with a coaxial extension and formed with a bore for passage of a lead therethrough, said lead passage of said clamping means being in registry with said bore. 